Fluid-conveying hose assemblies are ubiquitous in everyday life. Often, such assemblies convey caustic, corrosive, or volatile materials, such as fuel and fuel additives. In addition, such hose assemblies are often exposed to extreme operating temperatures and internal fluid pressures. Thus, it is desirable for such hose assemblies to be resistant to the chemical, environmental, and physical stresses to which they will be subjected.
Vehicle hose assemblies are particularly subject to extreme operating conditions. Fuel lines, for example, must be able to negotiate the tight tolerances, tortuous paths, and exacting dimensions of modern vehicles to carry fuel from the fuel tank to the engine. They must withstand both the pressure of the fuel therein and the high operating temperatures of the vehicle's engine compartment. In addition, the fuel line must be chemically resistant to the fuel, lest the assembly degrade and fail.
Regarding chemical resistance to fuel, it is known that polymeric fluorocarbon materials such as polytetrafluorethylene (PTFE) possess the requisite resistance for most fuel hose applications. Regarding structural strength and flexibility (that is, the ability to contain fluid under pressure and conform to vehicle dimensions), it is also known to braid fibers, such as stainless steel or nylon, about the inner core of the hose assembly to improve the kink-resistance of the hose assembly, improve the bend radius of the hose assembly, add tensile strength to the hose assembly, and increase the hoop strength of the hose assembly. For example, U.S. Pat. No. 5,655,572 (“the '572 patent”) and U.S. Pat. No. 6,257,280 (“the '280 patent”), both to Marena, disclose hose assemblies having a PTFE inner core, a first braided reinforcing layer with an interspersed organic polymeric material, and a braided outer liner. It is also known to improve flexibility through the use of a convoluted hose, such as disclosed in U.S. Pat. No. 3,023,787 to Phillips et al.
Given the volatility of fuel, temperature resistance is of high importance in a hose assembly installed as a fuel line. This is especially true in racing vehicles, which generally utilize more volatile fuels in an effort to improve engine performance and achieve higher speeds. In addition, in order to improve aerodynamics, racing vehicles are deliberately modified to impede the flow of air through the engine compartment by obstructing openings that would otherwise be present. These modifications force the vehicle closer to the road surface. The concomitant loss of convective cooling, however, substantially increases the temperature within the engine compartment.
Extant hose assemblies do provide some degree of thermal protection. For example, the '572 patent and the '280 patent utilize heat resistant glass fibers in the first reinforcing layer. The extremely high engine compartment temperatures in racing vehicles, however, can overcome the insulating properties of extant hose assemblies, thus vaporizing the fuel in the fuel lines, thereby potentially causing engine failure (vapor lock) and other undesirable conditions. It should be understood that this problem is not unique to fuel lines, but rather is faced by any volatile fluids present in the engine compartment, including, but not limited to, transmission fluid, brake fluid, and motor oil.
Accordingly, it is desirable to provide a hose assembly that is capable of preventing the fluid therein from vaporizing under the extremely high operating temperatures present in the engine compartment of a racing vehicle.